2020-12-29 15:05:33 +01:00
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# PlanckForth: Bootstrapping Forth from Handwritten Executable
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2020-12-28 14:11:20 +01:00
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2021-01-02 05:07:29 +01:00
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This project aims to bootstrap a Forth interpreter from hand-written tiny ELF binary.
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2021-01-02 05:01:31 +01:00
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## How to build
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You can create a binary for x86 linux environment by following steps.
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Only `xxd` is needed to build PlanckForth.
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2020-12-28 14:11:20 +01:00
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```
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2020-12-30 11:41:21 +01:00
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$ git clone https://github.com/nineties/planckforth.git
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$ cd planckforth
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2020-12-28 14:11:20 +01:00
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$ make
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2021-01-02 05:01:31 +01:00
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xxd -r -c 8 planck.xxd > planck
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chmod +x planck
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```
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## Hello World
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The hello world program at the beginning looks like this.
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```
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2021-01-02 05:15:42 +01:00
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$ ./planck
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2021-01-02 05:01:31 +01:00
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kHtketkltkltkotk tkWtkotkrtkltkdtk!tk:k0-tQ
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```
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2021-01-02 05:06:35 +01:00
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After bootstrapping by `bootstrap.fs`, it looks like this.
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2021-01-02 05:01:31 +01:00
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```
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$ cat bootstrap.fs - | ./planck
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." Hello World!" cr
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bye
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2020-12-29 06:51:27 +01:00
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```
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2020-12-28 18:16:46 +01:00
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# Builtin Words
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2021-01-02 01:29:30 +01:00
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| code | name | stack effect | semantics |
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|:----:|:---------|:----------------|:-----------------------------|
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| Q | quit | ( -- ) | Exit the process |
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| C | cell | ( -- n ) | The size of Cells |
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2021-01-02 01:30:51 +01:00
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| h | &here | ( -- a-addr ) | The address of 'here' cell |
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| l | &latest | ( -- a-addr ) | The address of 'latest' cell |
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2021-01-02 01:29:30 +01:00
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| k | key | ( -- c ) | Read character |
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| t | type | ( c -- ) | Print character |
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| j | jump | ( -- ) | Unconditional branch |
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| J | 0jump | ( n -- ) | Jump if a == 0 |
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| f | find | ( c -- xt ) | Get execution token of c |
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| x | execute | ( xt -- ... ) | Run the execution token |
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| @ | fetch | ( a-addr -- w ) | Load value from addr |
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| ! | store | ( w a-addr -- ) | Store value to addr |
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| ? | cfetch | ( c-addr -- c ) | Load byte from addr |
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| $ | cstore | ( c c-addr -- ) | Store byte to addr |
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| d | dfetch | ( -- a-addr ) | Get data stack pointer |
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| D | dstore | ( a-addr -- ) | Set data stack pointer |
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| r | rfetch | ( -- a-addr ) | Get return stack pointer |
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| R | rstore | ( a-addr -- ) | Set return stack pointer |
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| i | docol | ( -- a-addr ) | Get the interpreter function |
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| e | exit | ( -- ) | Exit current function |
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2021-01-02 01:30:51 +01:00
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| L | lit | ( -- n ) | Load immediate |
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2021-01-02 01:29:30 +01:00
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| S | string | ( -- c-addr u ) | Load string literal |
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| + | add | ( a b -- c ) | c = (a + b) |
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| - | sub | ( a b -- c ) | c = (a - b) |
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| * | mul | ( a b -- c ) | c = (a * b) |
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| / | div | ( a b -- c ) | c = (a / b) |
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| % | mod | ( a b -- c ) | c = (a % b) |
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| & | and | ( a b -- c ) | c = (a & b) |
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| \| | or | ( a b -- c ) | c = (a \| b) |
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| ^ | xor | ( a b -- c ) | c = (a ^ b) |
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| < | less | ( a b -- c ) | c = (a < b) |
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| = | equal | ( a b -- c ) | c = (a == b) |
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